As reflected in the patent literature, biaxial orientation of polyolefins produces films having applications in, for example, snack food packaging, cigarette overwrap, shrink film, electronic components wrapping, packaging tape, pressure sensitive tapes, labels, capacitor films, audio/video cassettes & CD overwrap, cable insulation and others. The polyolefins which may be employed in the preparation of biaxially oriented films include isotactic polypropylene homopolymers with high stereoregularity, although on some occasions the use of syndiotactic polymers has been proposed. Also suitable are co-polymers of isotactic polypropylenes with a small content of ethylene (mini-random co-polymers).
Biaxial polypropylene films have found wide acceptance in the packaging industry because of their superior physical properties such as high tensile strength, stiffness, optical clarity, gloss, and even a certain degree of moisture and oxygen resistance. Isotactic polypropylene homopolymers with higher stereoregularity not only possess enhanced mechanical properties, but also impart superior moisture barrier properties desirable especially for packaging industry. However, high isotacticity polypropylene materials are relatively more difficult to process for bi-axial stretching due to their high degree of crystallinity, and thus limiting oriented film productivity and quality. Manufacturers continue to develop polymer formulations that can be stretched more easily, which could translate into improved manufacturing efficiency as a result of factors such as decreased energy consumption and increased line speed. While many solutions have been proposed in the art to overcome the processing issue, such solutions often compromise the physical properties.
Therefore, it would be desirable to develop polymeric compositions that retain user-desired mechanical and/or physical properties while having an ease of processing.